Adhesion molecules in lily pollination

Adhesion occurs both between pollen tubes and between the pollen tube and t ransmitting tract epidermis (TTE) in lily. The stylar matrix secreted by th e TTE can be isolated and used in an in vitro adhesion assay for pollen tub es. This bioassay was used to isolate two stigma/stylar adhesion molecules in lily: a pectic polysaccharide and a small cysteine-rich, basic protein w e named SCA (stigma/stylar cysteine-rich adhesin). Both molecules were puri fied and used in an adhesion assay. Adhesion in the assay can be disrupted by treatment of the pectin with polygalacturonase and of SCA with proteinas e K. The two molecules bind to each other in a pH-dependent fashion, and th is binding is necessary for the adhesion assay to work. Antibodies to each of the molecules show their localization at the sites of pollen tube adhesi on in the style. Pollen does not produce SCA but does bind this protein in vivo and in vitro. In vivo functional analyses are necessary to establish t he roles of these molecules in lily pollination.